Ok so in the last week or two I have lost 7 copies, my ram and a rainbow fish. I lost two discus a little before this but thought they were a different reason. Now my Denison bard is on his way out it appears. There are no physical signs that I can tell. All the fish that have died, except one of the green copies which was half eaten when I found him in the morning, have looked perfectly healthy after death. They were all just fine the day before swimming and eating just fine. The next day either dead or in the case of the ram and Denison lying on the substrate gasping and every so often they swim in a spurt. Again as far as I can tell no physical symptoms. This is in my 125 that has been running as is since December and before that ran with gravel for 3 or 4 years. I stir the sand to make sure there are no gas bubbles. It is pool filter sand . 0,0,15 are water test results with API master kit pH 7.8 temp 78 to 79. Water changes every 3 to 4 days. Last one was done yesterday. Could this be columnaris? If so I see in the stickied article to use tetra fungus guard or jungle guard tabs. Is there some thing else? I am about to go to Petco to see if I can find something.